2009-13 LS3 Corvette Kooks Long-Tube Header System Install

Now We’re Kookin'

For more than a half-century, Corvette fanatics have been installing aftermarket headers and exhaust systems on their Vettes to increase power production and improve both sound and engine efficiency. Over time, the Corvette engineering team has also come to understand the benefits of a free-flowing exhaust, and this evolution has resulted in better and better factory manifolds and “X” crossover-pipe designs.

But as good as the stock parts are, sound-level requirements and production considerations still conspire to keep them from unleashing an engine's full potential. Fortunately, high-performance exhaust manufacturers such as Kooks Custom Headers are turning out show-quality systems that fit well and look the part while increasing power, torque, and aural fury. Best of all, thanks to the “turnkey” nature of these packages, you won't have to worry about leaks, rattles, poor fitment, or engine trouble codes.

To find out how easy a new Kooks long-tube header and crossover-pipe package is to install, we strolled over to AntiVenom EFI in Seffner, Florida, to follow along as the job was performed on an '11 Corvette Grand Sport. Equipped with a manual transmission and aftermarket mufflers, the GS laid down 409 horsepower and 401 lb-ft of torque on AntiVenom's DynoJet chassis dynamometer. Want to know how much a quality exhaust setup can add to that tally? Read on.

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2009-13 LS3 Corvette Kooks Long-Tube Header System Install

Our test Vette, an ’11 Grand Sport, was delivered to AntiVenom with a stock LS3 under the hood, a six-speed manual transmission, and a Corsa axle-back muffler system. It laid down an impressive 409.65 rwhp and 401.97 rwtq.

Our test Vette, an ’11 Grand Sport, was delivered to AntiVenom with a stock LS3 under the hood, a six-speed manual transmission, and a Corsa axle-back muffler system. It laid down an impressive 409.65 rwhp and 401.97 rwtq.

The four large primaries flow into a massive 3-inch header collector designed around a Kooks scavenging spike to ensure maximum flow and power.

Kooks also sent us a 3-inch “X” crossover system, which includes a set of the company’s high-flow Green catalytic converters. The latter carry 49-state emissions legality and keep your new Vette free of “check engine” lights.

Like the headers themselves, the X section is built from T304 stainless steel. It’s designed to bolt directly to a factory (or factory style) axle-back exhaust for a quick and easy upgrade.

Here you can see the factory system, which uses short, cast-iron manifolds and two catalytic converters to channel exhaust from the cylinder heads to the rear of the car. GM engineers have done an excellent job of optimizing this system, which flows well but could always perform even better.

The job begins with removing the four nuts (two per side) that attach the factory mid-pipe to the catalytic- converter down tubes. A 15mm socket is all you’ll need, though AntiVenom recommends spraying the bolts with some penetrating lubricant before cranking down on them.

The rear section of the mid-pipe simply slips over the factory axle-back section and is held in place by a single band on each side. Remove the nut, slide the band back on the mid-pipe, and you’re done. Head back up front, pull the mid-pipe back (another set of hands are helpful), and drop the mid-pipe from the vehicle.

The rear section of the mid-pipe simply slips over the factory axle-back section and is held in place by a single band on each side. Remove the nut, slide the band back on the mid-pipe, and you’re done. Head back up front, pull the mid-pipe back (another set of hands are helpful), and drop the mid-pipe from the vehicle.

Removing the catalytic converters is the next step, but don’t forget to unhook the rear oxygen sensors before pulling the assemblies. An 18mm open ended wrench will do the job; just take your time, as you’ll be reusing the sensors.

The catalytic converters bolt to the stock exhaust manifolds with two bolts, which can be difficult to access without the proper tools. An air-powered impact, a long extension, and a socket is how AntiVenom tackles this portion of the build, though you could do it with hand tools as well. Remove the two bolts, and you’re home free.

Time to head back up into the engine bay and work on removing the manifolds. AntiVenom’s Kyle Miller starts by pulling the factory engine covers and then removing the spark-plug wires to gain access to the plugs themselves. You’ll need them out of the way in order to slide the new headers in place.

Time to head back up into the engine bay and work on removing the manifolds. AntiVenom’s Kyle Miller starts by pulling the factory engine covers and then removing the spark-plug wires to gain access to the plugs themselves. You’ll need them out of the way in order to slide the new headers in place.

Removal the stock manifolds is fairly straightforward: Just six bolts hold each one to its corresponding cylinder head. See that upper bolt, second from the right? That just holds the heat shield in place, so you can leave it in and save yourself some time.

With the six bolts removed, Miller unclips the oxygen-sensor harness and lets the manifold rest in the engine bay while he raises the car. Then, it’s as simple as grabbing the manifold and pulling it out from the bottom.

A picture is worth a thousand words.

Installing the passenger-side header is an easy job from the bottom of the Grand Sport. Just guide it into place and let it rest on the engine cradle while you lower the car back down.

Kooks includes new aluminum exhaust-manifold gaskets with the header system; these slide between the laser-cut long-tube flange and the cylinder- head surface. These gaskets ensure a leak-free seal, so make sure you install them!

Pro Tip: A little antiseize goes a long way on the provided exhaust- manifold bolts. You’ll thank yourself later for taking the time to apply it to each one prior to installation. You don’t need a lot of the compound, just enough to coat the top five or six threads.

With the antiseize in place, Miller tightens down the exhaust-manifold bolts, starting with the centermost bolts and working outwards toward the ends of the cylinder heads. Get them snug but be careful not to over-tighten.

Install the driver-side header next, following the same steps previously outlined. It’s then time to move on to connecting the X crossover pipe, a job that begins with installing the provided oxygen-sensor extensions. These pre-terminated and heat-wrapped wires connect to the factory harness and the stock 02 sensors, giving them enough length to work with the longer headers.

AntiVenom recommends installing the rear oxygen sensors in the crossover pipe before bolting the assembly into the car. Here, you can see Miller sliding the pipe up into the axle-back section of the exhaust. Note the Green catalytic converters, which will keep emissions low, prevent any unwanted smells, pass inspection, and coexist happily with the engine computer.

With either stock or stock-dimension axle-back systems, the crossover pipe simply slides in place with a slip-fit connection. Just make sure you slide the clamps onto the pipe first, before you get everything connected.

Up front, the Kooks long-tube headers connect to the X crossover using a ball-and-socket flange and two bolts per side. Take your time tightening these connections, as you want to make sure you achieve a tight seal and proper fitment.

Once installed, the Kooks system fit as well as the factory parts and looked like a million bucks. The stainless steel won’t rust or corrode, so the exhaust will look this good for the rest of its life. Of course, the real question is, How well did it perform?

How do 418.66 rwhp and 410 rwtq of torque sound? Well, through the new pipes they actually sounded pretty great, but the gains alone speak for themselves. Down at 3,000 rpm, the dyno showed a jump of 11 lb-ft, which is something you can really feel on the street. The torque curve was elevated throughout the entire rpm band, and hp followed suit, up 9 horses at peak and even more from 5,000 to 6,000 rpm. With a basic complementary PCM tune, these numbers would have climbed even higher.

The all-new BBK Performance C6 long tube headers are the optimal alternative for your C6 Vette! Built from 304 stainless steel, these headers feature 1 and 3/4-inch primaries and fit 2005 and 2007 LS2 Corvettes, as well as 2008 and 2009 LS3 Corvettes! Also check out BBK's matching X crossover pipes and much more, at Vette Magazine! » Read More